Jet-lag is one of society's most prevalent disorders. Symptoms include insomnia, daytime sleepiness, fatigue, decrements in alertness and performance, dysphoric mood, loss of concentration, disorientation, and gastrointestinal distress. Jet-lag is not just the bane of tourists; it can impair the judgment and performance of businessmen and women, diplomats and the military. The symptoms of jet-lag occur because the internal circadian clock is slow to re-entrain to the sleep/wake schedule required in the new time zone. When several time zones are crossed, travelers are forced to sleep at the "wrong" phase of their circadian cycle, when they are physiologically set for waking, and then try to stay awake when they are physiologically set to sleep. As the circadian clock gradually phase shifts to re-entrain, the symptoms of jet-lag gradually dissipate. It takes longer to adapt after an eastward that after a westward flight, because the circadian clock is slower to advance than to delay. Furthermore, after an eastward flight, circadian rhythms may re-entrain in the wrong direction, e.g., they may delay 16 hrs instead of advancing 8 hrs, further prolonging the symptoms of jet-lag. The investigators propose to test treatments to phase advance the circadian clock before an eastward flight, in order to prevent or reduce the symptoms of jet-lag. The treatments will include 3 days of a gradually advancing sleep schedule, bright artificial light after waking, and afternoon melatonin pills. These treatments are specifically designed to be feasible for real travelers to use at home before a flight. The outcome measures will be the magnitude of phase advance on the day that corresponds to the day of flight, measured from the circadian rhythm of endogenous melatonin secretion. They will also measure the side effects of treatment, the "price" that travelers would have to pay in order to prevent or reduce jet-lag, including sleep loss (from wrist activity monitors and sleep logs) and daytime sleepiness and fatigue (from questionnaires). The goal is to develop practical recommendations for real travelers.